X-ray windows can be used for enclosing an x-ray source or an x-ray detector. In order to expose the x-ray detector to x-rays coming from multiple angles, it can be important to dispose the x-ray detector close to the x-ray window. The x-ray detector is typically disposed in an evacuated enclosure. The window can be used to separate ambient air from a vacuum within the enclosure.
X-ray windows can be made of a thin film. It can be desirable to minimize attenuation of the x-rays (especially with low energy x-rays), thus it can be desirable that the film is made of a material and thickness that will result in minimal attenuation of the x-rays. Thinner films attenuate x-rays less than thick films. The film cannot be too thin; however, or the film may sag or break.
A broken film can allow air to enter the enclosure, often destroying the functionality of the device. A sagging film can result in cracking of corrosion resistant coatings or allow the x-ray window to touch the x-ray detector. Thus it can be desirable to have a film that is made of a material that will have sufficient strength to avoid breaking or sagging, but also as thin as possible for minimizing attenuation of x-rays.
If the x-ray window is used with an x-ray detector, in order to avoid contamination of an x-ray spectra from a sample being measured, it can be desirable that x-rays impinging on the x-ray detector are only emitted from the source to be measured. Unfortunately, x-ray windows can also fluoresce and thus emit x-rays that can cause contamination lines in the x-ray spectra. Contamination of the x-ray spectra caused by low atomic number elements is usually less problematic than contamination caused by higher atomic number elements. It can be desirable therefore that the window and support structure be made of materials with as low of an atomic number as possible in order to minimize this noise.
It can also be important for x-ray windows to block visible and infrared light transmission, in order to avoid creating undesirable noise in sensitive instruments, such as an x-ray detector for example.
Information relevant to attempts to address these problems can be found in U.S. Pat. No. 5,090,046.